It is known from German Patent Specification No 21 61 885 to use a tool such as a punch to form a recess in part of the glass which has been forced out of the mould, the diameter of the recess being equal to that of the blowpipe, by the action of the tool on the glass. The form of the tool is such that the glass driven out from the mould by the punch is pressed into an annular recess in the punch tool.
After being thus pressed, the glass gob is delivered to this blowpipe by inserting the blowpipe into the recess. This process, however, has the disadvantage in that when the blowpipe is inserted for attachment to the glass gob, the pressure that can be produced at the blowpipe/glass contact surface is small, since the glass can escape outwards away from the blowpipe/glass interface thereby preventing the build-up of pressure necessary for an effective attachment of the blowpipe to the glass gob.
Furthermore, with this known arrangement the blowpipes/glass interface contact surface is too small to enable heavy gobs to be held on the blowpipe. Thus the requisite adherence between the blowpipe and the glass is difficult to attain, so that the blowpipe has to be variably pressed into the glass, sometimes deeply and sometimes less deeply into the glass to achieve the requisite adherence.
In this known process the blowpipe bore often becomes clogged by the glass. Consequently, an orderly and economic operation becomes impossible or very difficult.
German Patent Specification No AS 293 169 discloses a method in which a semi-finished glass object having an open side is formed with one or more projecting adhesive edges at the open side, the edges being connected to an attachment or mounting plate provided at the end of a blowpipe, which plate is flush with the end of the blowpipe tube. However, the contact surface is so small that heavy glass gobs cannot be reliably held upon the blowpipe.